1. Field of the Invention
The present invention relates to a process for forming images which comprises utilizing the photosensitive properties of a high molecular weight substance which is synthesized by homopolymerizing a monomer having two different kinds of functional groups which have different reactivity, that is, an acryloyl or methacryloyl group and a cinnamoyl group, or copolymerizing such monomer.
2. Description of the Prior Art
Hitherto, it has been known that cinnamic acid and esters thereof cause a photo-cross linking reaction by the action of rays to form a cyclobutane ring. Further, processes for forming images which comprise utilizing changes in solvent resistance and hardness by such a photo-cross linking reaction have also been examined. For example, see "Light Sensitive Systems", page 140, written by J. Kosar, published by John Wiley & Sons Co., 1965.
However, as described in detail in the above-mentioned reference, prior processes for the synthesis of photo cross-linkable materials have been carried out by a method which comprises producing an ester from polyvinyl alcohol having hydroxyl groups on the main chain as the starting material. This is a process for producing a polymer which has properties different from the starting material by reacting polyvinyl alcohol having reactive groups with another reagent, which is generally called a high molecular weight reaction. However, this reaction does not proceed quantitatively at the introduction of the active groups into the high molecular weight substance because of the so called high molecular weight effect. (Refer to, for example, 1. "Chemical Reactions of Polymers", page 1, written by E. M. Fettes, published by Interscience Pub. 1964; and 2. "Kindai Kogyo Kagaku" No. 16, a first volume, page 365, written by Iwakura et al, published by Asakurashoten, 1966).
The relationship shown in the drawing between the degree of substitution of a polymer into which cinnamic acid groups are introduced by the above-mentioned high molecular weight reaction and the ease of photo-cross linking is known. It is thus expected to synthesize a polymer containing cinnamoyl groups, in other words, a polymer having a reactive group per monomer unit of the synthesized polymer.
Much research has been done on the above system. For example, G. Smets, R. Hart and Kawai have individually examined the polymerization of vinyl monomers having a cinnamoyl group (vinyl cinnamate). However, according to their research, while vinyl cinnamate is easily subjected to ring-polymerization the produced polymer contains only approximately 20% cinnamic acid groups, and the polymer becomes insoluble in solvents because of gelation if the degree of polymerization of the polymer is raised so much. Recently, Kato examined polymers into which --O--C.sub.2 H.sub.4 or ##STR1## was introduced between the vinyl group and the cinnamoyl group and synthesized such polymers by a cationic polymerization reaction. However, a polymer having a high molecular weight cannot be obtained by a radical polymerization using this process. (Refer to, for example, "Polymer Sci." B(7) 605 by Kato (1969)).
G. Smets et al tried to synthesize the light sensitive resin directly from the radical polymerization, subsequent to synthesizing a cinnamic acid vinyl monomers. ##STR2## The polymerization is mainly proceeded in the ring mechanism and only those having low light sensitivity are obtained due to the small amount of cinnamic acid groups residing on the main chain of the polymer. In the process of the present invention, there can be obtained those having an excellent light sensitivity due to the cinnamic acid totally residing therein.
Kato et al produces the light sensitive resin in accordance with the following reaction system. ##STR3## In the radical polymerization, the intrinsic viscosity does not rise and those having low light sensitivity are obtained.
In accordance with the process of the present invention, the radical polymerization quickly proceeds and there is obtained resins having high light sensitivity.